It is known in the art that most common fuels contain some non-combustible impurities. The amount is generally negligible in refined fuels such as natural gas and distillate oils and may be less than about 1% in some residual oils. The solid state non-combustibles in fuel are referred to as mineral matter, whereas the material remaining after combustion is known as ash. Combustion processes that employ fuels comprising a relatively large amount of mineral matter may suffer from problems such as slagging, fouling and corrosion of the combustion chamber and associated components. In such processes, there has been much research into chemicals and additives that can correct or alleviate the problems. One such additive is bentonite.
Bentonite is a natural clay of the smectite family consisting primarily of montmorillonite, a hydrous aluminum silicate comprising a unit cell structure Si—Al—Si, and comprising a plurality of ionic materials. There are many different types of bentonites differing primarily in the type of ionic materials that are associated with molecular structure of the material. The crystalline lattice of most clays may have a portion of the aluminum atoms replaced with other metals in minor amounts including iron, zinc, nickel, lithium, calcium, sodium, magnesium and iron. For example, sodium bentonite and calcium bentonite differ by the amount of sodium and calcium cations replacing aluminum in the montmorillonite crystalline lattice. The differences in the molecular makeup between bentonites account for the wide variation in the molecular properties of these materials. For instance, sodium bentonite swells considerably in water whereas calcium bentonite does not. These differences also account for the variation in the industrial use of these materials. For example, certain bentonites may be used as a bonding material in the preparation of molding sand for the production of iron and steel castings, as a binding agent in the production of iron ore pellets, as a thixotropic material and lubricating agent in filling and drilling applications and also as a clumping agent in cat litter.
U.S. Pat. No. 4,159,683 discloses a method of reducing slag and soot formed from combustion of carbonaceous waste materials in furnaces by adding a small amount of sodium bentonite to the carbonaceous waste (fuel) of the combustion process.
U.S. Pat. No. 3,628,925 discloses a method of promoting combustion and reducing slag deposition, by including an adjuvant comprising calcium based montmorillonite clay with a hydrocarbon fuel.
U.S. Pat. No. 3,738,819 discloses the use of a combustion adjuvant comprising a calcium based montmorillonite clay, a phosphate and a source of boron oxide combined with a hydrocarbon fuel in a combustion zone.
There is a need in the art to increase the efficiency of combustion processes.